On a 1996 explorer Do you need special plug for the factory trailer wiring?
No, the 1996 Ford Explorer's factory trailer wiring harness uses a standard 4-way or 7-way connector. You don't need a special plug *unless* your trailer's connector is damaged or of a non-standard type. The factory harness will have either a 4-pin connector for basic lighting or a 7-pin connector for more extensive trailer functions (like brakes). You should simply need a matching connector on the trailer end.